Fall and Rise: The Story of 9/11: A gripping biography of triumph over tragedy

by Mitchell Zuckoff

Also worrisome were the techniques used to stop or at least slow a fire from weakening the spindly steel frames that supported the towers’ floors. Because the floor system was so original, neither the new nor the old New York City codes included regulations that addressed the engineers’ plans to use sprayed-on fire retardants. Special tests could have determined those answers, but no one conducted them. In the end, Port Authority officials essentially guessed at what type of fire-resistant material to use and how much to apply to prevent the steel floor supports from buckling in a blaze. Initially, they insisted that the fireproofing was adequate, and that each floor was built to be airtight. If a fire did break out, they said, it would be locally contained and cause limited damage. Later, however, they installed a sprinkler system, too.